Electrical apparatus.



R. A. FBSSENDEN.

ELECTRICAL APPARATUS. APPLIUATION FILED 23.18, 1906.

962,017., Patented June 21,1910.'

BEGINALD IA. FESSENDEN, OF IBRANT ROCK, IMASSACIIUSTTS,

nnncraronr. nrrannrtrs.

Specification of Letters Patent- Patented June 21, 1910.

Application ledApril 18, 1906. Serial No. 312,520,

To all whom 'it may concern:

Be it known that I, REGINALD A. FnssnN- DEN, a citizen of the UnitedStates, residing at Brant Rock, in the State of Massachusetts, haveinvented certain new and useful Im rovements in Electrical-Apparatus, of

' Whlch the following is a specification.

The invention comprises certain improvements in current-operateddevices, which are especially ada ted for use in connection withcurrents of hlgh frequency such as are employed in the transmission ofenergy by kelectro-magnetic waves. y

The invention is' herelnafter more fully described and claimed.

In the accompanying drawings, forming a part of this specification,Figure l is a diagrammatic view illustrative of va form of my invention;and Figs. 2, 3 and 4`are similar views illustrating other embodiments ofthe improvement.

Many electrical-indicating instruments were wound with coarse wire andformed of coils of large diameter, such, for example, as the tangentgalvanometer. Later,Lord Kelvinand others constructed instruments havinggreatly increased sensibility by-winding the coils oit' much iuer wireand using a larger number .of turns. The rlhomson galvanometer was anexample of such 1mproved instrument. The limit was, however, reached inthis direct-ion, on account of the high resistance of the wire and thefact that increasing the number of turns brought the outside turns sofar away from the core or axis that they produced no good eli'ect.

l have found it possible by making a radical change in the constructionof currentoperated instruments to obtain a very large increase insensibility. rlhis change involves abandoning the large diameter of thecoil used by Kelvin and others, by constructing my coils of what mi htbe called microscopic and microbaric imensions, since as a rule they arebest wound under a microscope. As illustrating the radical change eectedby my improvement, the coil of a Thomson galvanometer is usually aboutfour inches in diameter and .one inch in thickness, whereas .a suitablesize of coil for what I call my micro instrument is about four.one-hundredths of an inch in diameter and one one-hundredth of an inchin thickness. The relative volumesjof the coils are in the ratio .ofonel to one million. These coils not only furnish very suitableinstruments for ordinary uses, but lare especially and peculiarlyadapted to signalin by electro-magnetic waves, for the `reason. t atthese microscopic coils concen.

trate the magneticefects to such a great degree that the opposition tothe current due to self-induction 1s considerably greater than theopposition to the current due to ohmic resist-ance, and hence the coilsact very eiliciently and are capable of sharp tuning.

As an illustration of the enormous advantages to be gained by the use ofcoils of these y extremely tine 'laminated iron wire cores 1n thesecoils, the laminated iron wire being preferably about one one-thousandthof an inch in diameter, or such thatten of them twisted together willform the thickness of a human hair. v

An additional advantage is obtained where the coil itself forms one ofthe moving members of a' current-operated device. If such a microbariccoil be attracted by another similar coil, it is found that the amountof movement taking lace in a given time decreases with a very igh owerof the diameter of the wire used, an halving the sizeJ of the wire themovement taking place in a given time may be increased more than onehundred times.

ln the construction shown in Fig. l, the aerial indicated at l isgrounded'` at 2.

Micro coils 3 and 4, preferably supported Iso as to be adjustable, areoperatively conone end with smallcores l1 and 12 formed elo that by ofsoft iron or nichel-wire, ahdfpr'eferabl consisting of about fiftypieces o wire ea of about one one-thousandth of an inch in diameter. Thecoils 3 and 4 are preferably wound with wire one one-thousandth of aninch in diameterv so as to have about fty lacquer, or cellulose. Attheir opposite ends the needles 7 and 8 are preferablyA provided withline platinum iridium contacts 13 and 14, between which is arranged awedge 15 preferably of similar material and a apted to be adjusted by ascrew 16. A local 'circuit is formed by the battery 17 and indicating emechanism 18, the wires 5 and 6, needles 7 and 8, and wedge or contact15.

In the operation of this apparatus the lthe screws 9 and 10 are turned4until the natural periods of vibration of the needles 7 and 8 carriedby said wires are equal, and

.preferably equal to the group-frequency of the signals which it isdesired to receive.,

The contact piece 15 is then .adjusted so las nearly to make contactwith the points 13 and 14 carried bythe needles. Thecoils 3 and 4 areadjusted to such osition as to produce a maximum effect on oth themovable cores 11 and 12. A fixed core may also be used for increasingthe s ensitiveness of the device as arranged in Fig. 2. 'The receiver,consisting o f the micro-coils 3 and 4, may be tuned in any of the usualways practiced in the art, as, for example, by a variable condenser 19.A

Should any mechanical vibration disturb the receiver, both needles 7 and8 will move in the same direction, and hence only one of them will makecontact with the wedge l5, and the local circuit will not be closed.When, however, waves strike the aerial 1, the currents produced in themicro-coils 3 and 4 will attract the movable cores 11 and 12, causingboth contacts 13 and 14 to bear against the wedge 15 and so close thelocal circuit containing the indicating mechanism 17.

When desired, any suitable arrangement of the contacts and circuits maybe used, uch, for example, as that indicated in Fig.

As indicated at 37 in Fig. 1, a mirror may be employed forindicatingsignals in lieu of the local circuit, such mirror be' attached to one orthe other of the nec es 7 and 8.

In Fig. 2, vmy improvement is shown applied to a telephone indicatingmechanism. A micro-coil l23, as shown in section and preferably made asabove described, is secured to the telephone diaphragm 22 and isconnected to the aerial 1. Another microcoil 26 i's seeured to a mount27 and is cohnected to the coil 23, and also to round, as shown. Themount 27 is adjuste by means of a screw or other suitable means so as tobring the coils 23 and 26 in the most effective relation to each other.When the eurrent is generated b the action of electromagnetic waves of te aerial, the coils 23 an '26 will attract each other, causing thediaphragm to move, thereby producing a sound.

In the construction shown in Fig. 3 for simllar purposes, the coils 29and 30 are secured to diaphragms 31 and 32, (the diaphragm 32 being1similar to a telephone diaphragm, while t e other diaphragm is madesufficiently heavy to prevent moyement of vthe coil attached thereto)arranged in a resonator-tube'34, said tube being provided 'with aistonadjustable by a screw 35, so as yto pro uce resonance to anydesired groupfrequency.' In this construction, the removable core isomitted and the fixed coil, which may have a fixed core, preferablyprojecting into the movable coil, acts on the movable coil, which ispreferably smaller than thel fixed coil. The tube is provided with aphonographic ear-piece 36, which may be mserted in the ear as iscustomary in using these devices, and loss of sound thereby revented. Asshown in Fig. 4, a plurality of micro-coils 38 may be used, said coilsbeing arranged in pairs. In the construction, the needles 39 are securedto a common wire 40, which is placed under tension, asin theconstruction shown in Fig. 1, and are provided attheir ends with cores42 arranged in operative Arelation to the coils. As an indicating'device, I emplo a minute capillary glass tube 43 secure 'to the wire 40,ysaid tube being provided ar its end with small pieces of mirror 44.Such an ar-9 rangement of mirrors, if given suicient illumination, is caable of resolving to the same extent as a arge mirror. The effect of anylack of` arallelism in the small mirrors 1s remov by any of thewell-known arrangements of prisms or mirrors. A local circuit adjustablein stre may be used in conjunction with this orm of cur-`rent-responsive device and gives greater ease ,l

i ity. Such local of adjustment and sensib circuit is shown in F' 4,where 45 is alocal source of current an 46 adjustable resistance.

It is characteristic of my invention that I employ a microbaric coil, z.e.-a coil of vsmall wireso wound as to produce a relatively highmagnetic concentration for a 'ven current, a given llliifthof wire, an agiven mass, as com a with coils ordinarily used for electricainstruments. That is, 1n my claims the terms microbaric coil largecoetlicient of induction per unit mass, and high intensity of magneticinduction per aorr unit mass and unit of entrent, mean these quantitiesare of high order of magnitude compared with coils now in use, as in U.S. Patents 711,445 of Oct. 14th, 1902 and 711,184 (see p. 3, line 104).

, ing an indication comprising a coil of such small dimensions as togive the coil a ratio of magnetic induction per unit of mass of theorder of 100,000..

3. Electrically actuated means for producing an indication, comprising acoil having a high magnetic concentration and a co-eiiicient of magneticinductance per unit of mass greater than 100,000.

4. Electrically actuated means for producing an indication comprisingamovable indicating member and a coil 1n operative relation to saidmovable member, having high co-eicient of magnetic inductance per unitof mass e. e., a ratio of self inductance fo mass `of more than 100,000.

5. Electrically actuated means for producing an indication comprising acoil having a ratio of self-induction to mass, greater than 100,000, amovable element, controlling a of which one is attache local circuit,and means in the local circuit p for producing an indication.

6. A receiver for electro-ma etic waves comprising two relativel mova leelements, to a coil having a large co-eiicient of magnetic induction perunit of mass of the order 100,000.

7. A 'receiver for electro-magnetic waves comprising a microbaric coiland` a movable core therefor and indicating means operated by the motionof the core.

8. A receiver for wireless telegraphy comprising a solenoid of which thecoil is o f minute relative dimensions having high magneticconcentration per unit of mass and per turn so as to respond to signals,substantially as described.

9. A receiver for wireless signaling comprising several relativelymovable members, an indicating device attached to onevof said members,and onevof said members includin a microbaric coil of minute dimensions,o the order of magnitude of .001 of an inch for the wire, whereby highmagnetic concentration suiicientto respond to electro-magneticoscillations is obtained.

In testimony whereof, I set my hand.

REGINALD A. FESSENDEN.

lVitnesses:

Roar. S. KEARNEY, DARWIN S. WoLco'r'r.

have hereunto

